Method and apparatus for data transmission and reception for network coordinated communication

ABSTRACT

The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method and an apparatus for transmitting and receiving data for coordination communication is provided.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. §119(a) of a Korean patent application number 10-2019-0003521, filed onJan. 10, 2019, in the Korean Intellectual Property Office, thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a wireless communication system. Moreparticularly, the disclosure relates to a method and an apparatus fortransmitting and receiving data between a terminal and a plurality oftransmission nodes performing coordinated communication in order tosmoothly provide a service.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th-Generation (4G) communication systems, efforts havebeen made to develop an improved 5th-Generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post long-term evolution(LTE) System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), Full Dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud Radio Access Networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,Coordinated Multi-Points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid Frequency-Shift Keying (FSK) andQuadrature Amplitude Modulation (QAM) (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

With the development of communication systems, studies are activelybeing conducted on processes of exchanging data between a plurality ofnodes performing network coordinated communication and a terminal.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea wireless communication system and, more particularly, to a method andan apparatus for efficiently transmitting data between a terminal and aplurality of transmission nodes performing coordinated communication.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, when network coordinatedcommunication is used in a wireless communication system, it is possibleto reduce reception hardware complexity and computational complexity ofa terminal. In addition, when network coordinated communication is used,it is possible to reduce interference in a terminal by differenttransmission and reception nodes, thus efficiently performing networkcoordinated communication.

In accordance with an embodiment of the disclosure, a method performedby a terminal comprises: receiving, from a first transmission andreception point (TRP), first downlink control information (DCI)scheduling a first physical downlink shared channel (PDSCH)transmission; receiving, from a second TRP, second DCI scheduling asecond PDSCH transmission, wherein the second PDSCH transmissionoverlaps with the first PDSCH on a time-frequency resource; andreceiving the first PDSCH transmission and the second PDSCH transmissionbased on a first demodulation reference signal (DMRS) associated withthe first PDSCH transmission and a second DMRS associated with thesecond PDSCH transmission, wherein the first DMRS and the second DMRSare received on a same location within the time-frequency resource.

In accordance with an embodiment of the disclosure, a method performedby a first transmission and reception point (TRP) comprises:transmitting, to a terminal, first downlink control information (DCI)scheduling a first physical downlink shared channel (PDSCH)transmission; and transmitting, to the terminal, the first PDSCHtransmission based on a demodulation reference signal (DMRS) associatedwith the first PDSCH transmission, wherein second DCI scheduling asecond PDSCH transmission is transmitted to the terminal from a secondTRP, wherein the second PDSCH transmission is transmitted to theterminal based on a second DMRS associated with the second PDSCHtransmission, wherein the second PDSCH transmission overlaps with thefirst PDSCH transmission on a time-frequency resource, and wherein thefirst DMRS and the second DMRS are transmitted on a same location withinthe time-frequency resource.

In accordance with an embodiment of the disclosure, a terminalcomprises: a transceiver configured to transmit and receive a signal;and a controller configured to: receive, from a first transmission andreception point (TRP), first downlink control information (DCI)scheduling a first physical downlink shared channel (PDSCH)transmission, receive, from a second TRP, second DCI scheduling a secondPDSCH transmission, wherein the second PDSCH transmission overlaps withthe first PDSCH on a time-frequency resource, and receive the firstPDSCH transmission and the second PDSCH transmission based on a firstdemodulation reference signal (DMRS) associated with the first PDSCHtransmission and a second DMRS associated with the second PDSCHtransmission, wherein the first DMRS and the second DMRS are received ona same location within the time-frequency resource.

In accordance with an embodiment of the disclosure, a first TRPcomprises: a transceiver configured to transmit and receive a signal;and a controller configured to: transmit, to a terminal, first downlinkcontrol information (DCI) scheduling a first physical downlink sharedchannel (PDSCH) transmission, and transmit, to the terminal, the firstPDSCH transmission based on a demodulation reference signal (DMRS)associated with the first PDSCH transmission, wherein second DCIscheduling a second PDSCH transmission is transmitted to the terminalfrom a second TRP, wherein the second PDSCH transmission is transmittedto the terminal based on a second DMRS associated with the second PDSCHtransmission, wherein the second PDSCH transmission overlaps with thefirst PDSCH transmission on a time-frequency resource, and wherein thefirst DMRS and the second DMRS are transmitted on a same location withinthe time-frequency resource.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and its advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a transmission structure in a time-frequency domainof an LTE, LTE-A, or NR system or a similar wireless commutation systemaccording to an embodiment of the disclosure;

FIG. 2 illustrate structures of a frame, a subframe, and a slot in 5Gaccording to an embodiment of the disclosure;

FIG. 3 illustrates an example of the configuration of a bandwidth partaccording to an embodiment of the disclosure;

FIG. 4 illustrates an example of indicating and changing a bandwidthpart according to an embodiment of the disclosure;

FIG. 5 illustrates an example of a control-region configuration of adownlink control channel according to an embodiment of the disclosure;

FIG. 6 illustrates an example of frequency-domain resource allocation ofa physical downlink shared channel (PDSCH) according to an embodiment ofthe disclosure;

FIG. 7 illustrates an example of time-domain resource allocation of aPDSCH according to an embodiment of the disclosure;

FIG. 8 illustrates an example of time-domain resource allocation of aPDSCH according to an embodiment of the disclosure;

FIG. 9 illustrates the protocol stacks of a base station and a UE whensingle cell, carrier aggregation, dual connectivity are performedaccording to an embodiment of the disclosure;

FIG. 10 illustrates examples of a coordinated-communication antenna portconfiguration and resource allocation according to an embodiment of thedisclosure;

FIG. 11 illustrates an example of the configuration of downlink controlinformation (DCI) for coordinated communication according to anembodiment of the disclosure;

FIG. 12 illustrates the priorities of PDSCHs in NR and the priorities ofPDSCHs according to an embodiment of the disclosure;

FIG. 13 is a flowchart illustrating a method for prioritizing PDSCHsscheduled in overlapping time resources according to an embodiment ofthe disclosure;

FIG. 14 is a flowchart illustrating a method for a UE to activate areceiver for only one of non-coherent joint transmission (NC-JT) andmulti-user multiple-input and multiple-output (MU-MIMO) in order toreduce complexity according to an embodiment of the disclosure;

FIG. 15 illustrates the structure of a terminal according to anembodiment of the disclosure; and

FIG. 16 illustrates the structure of a base station according to anembodiment of the disclosure.

The same reference numerals are used to represent the same elementsthroughout the drawings.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

In describing the embodiments, descriptions of technologies which arealready known to those skilled in the art and are not directly relatedto the disclosure may be omitted. Such an omission of unnecessarydescriptions is intended to prevent obscuring of the main idea of thedisclosure and more clearly transfer the main idea.

For the same reason, in the accompanying drawings, some elements may beexaggerated, omitted, or schematically illustrated. Further, the size ofeach element does not entirely reflect the actual size. In the drawings,identical or corresponding elements are provided with identicalreference numerals.

The advantages and features of the disclosure and methods of achievingthe same will be apparent by referring to embodiments of the disclosureas described below in detail in conjunction with the accompanyingdrawings. The disclosure is not limited to embodiments disclosed belowbut may be embodied in various forms. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the disclosure to those skilled in the art towhich the disclosure pertains. The disclosure is defined only by thescope of claims. Like reference numerals refer to like elementsthroughout.

Here, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions specified in the flowchart block or blocks.These computer program instructions may also be stored in anon-transitory computer usable or computer-readable memory that candirect a computer or other programmable data processing apparatus tofunction in a particular manner, such that the instructions stored inthe non-transitory computer usable or computer-readable memory producean article of manufacture including instruction means that implement thefunction specified in the flowchart block or blocks. The computerprogram instructions may also be loaded onto a computer or otherprogrammable data processing apparatus to cause a series of operationalsteps to be performed on the computer or other programmable apparatus toproduce a computer implemented process such that the instructions thatexecute on the computer or other programmable apparatus provide stepsfor implementing the functions specified in the flowchart block orblocks.

And each block of the flowchart illustrations may represent a module,segment, or portion of code, which includes one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

As used herein, the “unit” refers to a software element or a hardwareelement, such as a Field Programmable Gate Array (FPGA) or anApplication Specific Integrated Circuit (ASIC), which performs apredetermined function. However, the “unit does not always have ameaning limited to software or hardware. The “unit” may be constructedeither to be stored in an addressable storage medium or to execute oneor more processors. Therefore, the “unit” includes, for example,software elements, object-oriented software elements, class elements ortask elements, processes, functions, properties, procedures,sub-routines, segments of a program code, drivers, firmware,micro-codes, circuits, data, database, data structures, tables, arrays,and parameters. The elements and functions provided by the “unit” may beeither combined into a smaller number of elements, “unit” or dividedinto a larger number of elements, “unit”. Moreover, the elements and“units” may be implemented to reproduce one or more CPUs within a deviceor a security multimedia card. Further, according to some embodiments,the “unit” may include one or more processors.

Hereinafter, the operating principle of the disclosure will be describedin detail with reference to the accompanying drawings. In the followingdescription of the disclosure, a detailed description of knownconfigurations or functions incorporated herein will be omitted when itis determined that the detailed description may make the subject matterof the disclosure unclear. The terms as described below are defined inconsideration of the functions in the embodiments, and the meaning ofthe terms may vary according to the intention of a user or operator,convention, or the like. Therefore, the definitions of the terms shouldbe made based on the contents throughout the specification. Hereinafter,a base station is an entity that performs resource allocation for aterminal and may be at least one of a gNode B, an eNode B, a Node B, abase station (BS), a radio access unit, a base station controller, atransmission and reception point (TRP), or a node in a network. Aterminal may include a user equipment (UE), a mobile station, a cellularphone, a smartphone, a computer, or a multimedia system capable ofperforming a communication function but is not limited thereto.

Hereinafter, embodiments illustrate a technology for a terminal toreceive broadcast information from a base station in a wirelesscommunication system. As used in the following description, a termreferring to broadcast information, a term referring to controlinformation, a term related to communication coverage, a term referringto a state change (e.g., an event), terms referring to network entities,terms referring to messages, a term referring to a component of anapparatus, and the like are illustrated for convenience of description.Therefore, the disclosure is not limited by the following terms, andother terms having equivalent technical meanings may be used.

For convenience of explanation, some terms and words defined in thethird generation partnership project long term evolution (3GPP LTE)standard may be used. However, the disclosure is not limited by theseterms and words and may be equally applied to systems in accordance withother standards.

A wireless communication system is evolving from initially providingvoice-oriented services into a broadband wireless communication systemfor providing high-speed and high-quality packet data services accordingto a communication standard, for example, high speed packet access(HSPA), long-term evolution (LTE or evolved universal terrestrial radioaccess (E-UTRA)), LTE-advanced (LTE-A), or LTE-Pro of the 3GPP, highrate packet data (HRPD) or ultra mobile broadband (UMB) of the 3GPP2,and IEEE 802.16e.

As a representative example of a broadband wireless communicationsystem, an LTE system employs an orthogonal frequency divisionmultiplexing (OFDM) scheme for a downlink (DL) and employs asingle-carrier frequency division multiple access (SC-FDMA) scheme foran uplink (UL). The uplink refers to a radio link for a user equipment(UE) or a mobile station (MS) to transmit data or a control signal to aneNode B or a base station (BS), and the downlink refers to a radio linkfor the eNode B to transmit data or a control signal to the UE. Thesemultiple access schemes allocate and manage time-frequency resources forcarrying data or control information per user not to overlap with eachother, that is, to be orthogonal to each other, thereby dividing data orcontrol information for each user.

A post-LTE communication system, that is, a 5G communication systemneeds to be able to freely reflect various demands from users andservice providers and is thus required to support services satisfyingvarious requirements. Services considered for a 5G communication systeminclude enhanced mobile broadband (eMBB), massive machine-typecommunication (mMTC), ultra reliability and low latency communications(URLLC), and the like.

According to some embodiments, eMBB is intended to provide a furtherenhanced data rate than that supported by existing LTE, LTE-A, orLTE-Pro. For example, in a 5G communication system, for one basestation, eMBB needs to be able to provide a peak data rate of 20 Gbps ina downlink and a peak data rate of 10 Gbps in an uplink. Further, eMBBneeds to provide an increased user-perceived data rate. In order to meetthese requirements, improved transmission and reception technologiesincluding an enhanced multiple-input and multiple-output (MIMO)transmission technology are required. In addition, it is possible tosatisfy a data rate required for a 5G communication system by employinga frequency bandwidth wider than 20 MHz in a frequency band ranging from3 to 6 GHz or a 6-GHz frequency band or higher instead of a 2-GHz bandcurrently used for LTE.

In a 5G communication system, mMTC is taken into consideration tosupport application services, such as the Internet of Things (IoT). Toefficiently provide the IoT, mMTC may require support for access of agreat number of UEs in a cell, enhanced UE coverage, increased batterytime, reduced UE cost, and the like. The IoT is attached to varioussensors and various devices to provide a communication function and thusneeds to be able to support a large number of UEs (e.g., 1,000,000UEs/km²) in a cell. A UE supporting mMTC is highly likely to be locatedin a shadow area not covered by a cell, such as the basement of abuilding, due to the nature of services and may thus require widercoverage than for other services provided by the 5G communicationsystem. A UE supporting mMTC needs to be configured as a low-cost UE,and may require a very long battery life time because it is difficult tofrequently change the battery of the UE.

Finally, URLLC is a mission-critical cellular-based wirelesscommunication service, which is used for remote control of robots ormachinery, industrial automation, unmanned aerial vehicles, remotehealth care, emergency alerts, and the like and needs to provideultralow-latency and ultra-reliability communication. For example, aURLLC-supporting service is required not only to satisfy an airinterface latency of less than 0.5 milliseconds but also to have apacket error rate of 10⁻⁵ or less. Therefore, for the URLLC-supportingservice, a 5G system needs to provide a shorter transmission timeinterval (TTI) than that of other services and also requires a designfor allocating a wide resource in a frequency band. The foregoing mMTC,URLLC, and eMBB are merely examples of different service types, andservice types to which the disclosure is applied are not limited to theforegoing examples.

The foregoing services considered in a 5G communication system need tobe provided in a fusion with each other based on one framework. That is,for efficient resource management and control, it is preferable that theservices are controlled and transmitted as one integrated system ratherthan being operated independently.

Hereinafter, although embodiments will be described with reference to anLTE, LTE-A, LTE Pro, or NR system as an example, these embodiments mayalso be applied to other communication systems having a similartechnical background or channel form. Further, the embodiments may alsobe applied to other communication systems through some modificationswithout departing from the scope of the disclosure as determined bythose skilled in the art.

Hereinafter, a frame structure of a 5G system will be described indetail with reference to accompanying drawings.

FIG. 1 illustrates the basic structure of a time-frequency domain, whichis a radio resource region in which a data or control channel istransmitted in a 5G system according to an embodiment of the disclosure.

Referring to FIG. 1, the horizontal axis represents a time domain, andthe vertical axis represents a frequency domain. The basic unit of aresource in the time-frequency domain is a resource element (RE) 1-01,which may be defined by one orthogonal frequency division multiplexing(OFDM) symbol 1-02 on the time axis and one subcarrier 1-03 on thefrequency axis. In the frequency domain, N_(sc) ^(RB) (e.g., 12)consecutive REs may form one resource block (RB) 1-04. In LTE, LTE-A,and LTE-A Pro, two slots each of which includes seven OFDM symbols arecombined to form one subframe 1-10, and one subframe forms atransmission time interval (TTI) as a transmission unit in the timedomain.

FIG. 2 illustrate a slot structure considered in a 5G system accordingto an embodiment of the disclosure.

Referring to FIG. 2 illustrates one example of structures of a frame2-00, a subframe 2-01, and a slot 2-02. One frame 2-00 may be defined as10 ms. One subframe 2-01 may be defined as 1 ms. Therefore, one frame2-00 may include a total of ten subframes 2-01. One slot 2-02 and 2-03may be defined as 14 OFDM symbols slot (i.e., number of symbols per slot(N_(symb) ^(slot))=14), and one slot forms a TTI. One subframe 2-01 mayinclude one or a plurality of slots 2-02 and 2-03, and the number ofslots 2-02 and 2-03 per subframe 2-01 may vary depending on a setsubcarrier spacing value μ 2-04 and 2-05. In the example of FIG. 2, asthe set subcarrier spacing value, μ=0 (2-04) and μ=1 (2-05). When μ=0(2-04), one subframe 2-01 may include one slot 2-02; when μ=1 (2-05),one subframe 2-01 may include two slots 2-03. That is, the number ofslots per subframe (N_(slot) ^(subframe,μ)) may vary depending on theset subcarrier spacing value μ, and the number of slots per frame(N_(slot) ^(frame,μ)) may vary accordingly. N_(slot) ^(subframe,μ) andN_(slot) ^(frame,μ) according to each subcarrier spacing setting μ maybe defined as in Table 1.

TABLE 1 μ N_(symb) ^(slot) N_(slot) ^(frame,μ) N_(slot) ^(subframe,μ) 014 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16 5 14 320 32

In NR, one component carrier (CC) or serving cell can include up to 250RBs. Therefore, when a UE always receives the entire serving cellbandwidth as in LTE, the power consumption of the UE may be extreme. Tosolve this problem, a base station may configure one or more bandwidthparts (BWP) for the UE, thus supporting the UE in changing a receptionregion in the cell. In NR, the base station may configure an initialBWP, which is the bandwidth of control resource set (CORESET) #0 (or acommon search space: CSS), for the UE through a master information block(MIB). Subsequently, the base station may configure a first BWP for theUE through radio resource control (RRC) signaling and may report atleast one piece of BWP configuration information that may be indicatedthrough DCI in the future. The base station may report a BWP ID to theUE through DCI, thereby indicating a band for the UE to use. When the UEfails to receive the DCI in the currently allocated BWP for a specifiedtime or longer, the UE returns to a default BWP and attempts to receivethe DCI.

FIG. 3 illustrates an example of the configuration of a BWP in a 5Gcommunication system according to an embodiment of the disclosure.

Referring to FIG. 3 shows an example in which a UE bandwidth 3-00 isconfigured with two BWPs, that is, BWP #1 3-05 and BWP #2 3-10. A basestation may configure one BWP or a plurality of BWPs for the UE and mayconfigure information about each BWP as follows.

TABLE 2 Configuration information 1: Bandwidth of a BWP (the number ofphysical resource blocks (PRBs) included in the BWP) Configurationinformation 2: Frequency position of a BWP (e.g., an offset valuerelative to reference point A, in which the reference point may be, forexample, the center frequency of a carrier, a synchronization signal, asynchronization signal raster, or the like) Configuration information 3:Numerology of a BWP (e.g., subcarrier spacing, cyclic prefix (CP)length, or the like) Other information

In addition to the above pieces of configuration information, variousparameters related to the BWP may be configured for the UE. These piecesof information may be transmitted from the base station to the UEthrough higher-layer signaling, for example, RRC signaling. At least oneof the one configured BWP or the plurality of configured BWPs may beactivated. Whether to activate a configured BWP may be indicated fromthe base station to the UE semi-statically through RRC signaling ordynamically through a medium access control (MAC) control element (CE)or DCI.

The configuration of a BWP supported by the 5G communication system maybe used for various purposes.

In one example, when a bandwidth supported by a UE is smaller than asystem bandwidth, the configuration of a BWP may be used. For example,the frequency position of the BWP in Table 2 (configuration information1 in Table 2) may be set for the UE, enabling the UE to transmit andreceive data at a particular frequency position within the systembandwidth.

In another example, a base station may configure a plurality of BWPs fora UE in order to support different numerologies. For example, in orderto support data transmission and reception using both a subcarrierspacing of 15 kHz and a subcarrier spacing of 30 kHz for a UE, two BWPsmay be configured to use a subcarrier spacing of 15 kHz and a subcarrierspacing of 30 kHz, respectively. Different BWPs may be subjected tofrequency division multiplexing (FDM). When the UE intends to transmitand receive data with particular subcarrier spacing, a BWP configuredwith the subcarrier spacing may be activated.

In still another example, a base station may configure BWPs havingdifferent bandwidths for a UE in order to reduce power consumption ofthe UE. For example, when a UE supports a very large bandwidth, forexample, a bandwidth of 100 MHz, and always transmits and receives datain the bandwidth, the UE may consume great power. In particular, it isvery inefficient in power consumption that the UE unnecessarily monitorsa downlink control channel over the large bandwidth of 100 MHz even whenthere is no traffic. Therefore, in order to reduce power consumption ofthe UE, the base station may configure a BWP having a relatively smallbandwidth, for example, a BWP of 20 MHz, for the UE. The UE may performa monitoring operation in the 20-MHz BWP in the absence of traffic, andthe UE may transmit and receive data using the 100-MHz bandwidthaccording to an indication from the base station when the data isgenerated.

FIG. 4 illustrates a method of dynamically changing the configuration ofa BWP according to an embodiment of the disclosure.

As described in Table 2, a base station may configure one BWP or aplurality of BWPs for a UE and may report, as the configuration of eachBWP, information about the bandwidth of the BWP, the frequency positionof the BWP, and the numerology of the BWP. FIG. 4 shows an example inwhich two BWPs, which are BPW #1 4-05 and BWP #2 4-10, are configured ina UE bandwidth 4-00 for one UE. One or a plurality of the configuredBWPs may be activated, and FIG. 4 shows an example in which one BWP isactivated. Referring to FIG. 4, BWP #1 4-05 of the configured BWPs isactivated in slot #0 4-25, and the UE may monitor a physical downlinkcontrol channel (PDCCH) in control region 1 4-45 configured in BWP #14-05 and may transmit and receive data 4-55 in BWP #1 4-05. The controlregion in which the UE receives the PDCCH may vary according to whichBWP is activated among the configured BWPs, and thus the bandwidth inwhich the UE monitors the PDCCH may vary.

The base station may further transmit an indicator for switching theconfiguration of a BWP to the UE. Here, switching the configuration of aBWP may be considered the same as activating a particular BWP (e.g.,switching an activated BWP from BWP A to BWP B). The base station maytransmit a configuration switching indicator to the UE in a particularslot. After receiving the configuration switching indicator from thebase station, the UE may determine a BWP to be activated by applying achanged configuration according to the configuration switching indicatorfrom a particular time and may monitor a PDCCH in a control regionconfigured in the activated BWP.

Referring to FIG. 4, the base station may transmit a configurationswitching indicator 4-15 indicating a switch of the activated BWP fromexisting BWP #1 4-05 to BWP #2 4-10 to the UE in slot #1 4-30. Afterreceiving the indicator, the UE may activate BWP #2 4-10 according tothe content of the indicator. Here, a transition time 4-20 for a BWPswitch may be required for the UE, and the time to switch and apply aBWP to be activated may be determined according to the transition time.Referring to FIG. 4, a transition time 4-20 of one slot is requiredafter receiving the configuration switching indicator 4-15. Datatransmission and reception may not be performed in the transition time,that is, a guard period (GP) 4-60 may be set. Accordingly, BWP #2 4-10may be activated in slot #2 4-35, and thus the UE may transmit andreceive a control channel 4-50 and data 4-55 via the BWP in slot #2 4-35and slot #3 4-40.

The base station may pre-configure one BWP or a plurality of BWPs forthe UE via upper-layer signaling (e.g., RRC signaling) and may indicateactivation by mapping the configuration switching indicator 4-15 withone of BWP configurations preconfigured by the base station. Forexample, a log 2N-bit indicator may indicate one BWP selected from amongN preconfigured BWPs. Table 3 shows an example of indicatingconfiguration information about a BWP using a two-bit indicator.

TABLE 3 Indicator value BWP configuration 00 Bandwidth configuration Aconfigured via upper-layer signaling 01 Bandwidth configuration Bconfigured via upper-layer signaling 10 Bandwidth configuration Cconfigured via upper-layer signaling 11 Bandwidth configuration Dconfigured via upper-layer signaling

The foregoing configuration switching indicator 4-15 for the BWP may betransmitted from the base station to the UE via MAC CE signaling or L1signaling (e.g., common DCI, group-common DCI, or UE-specific DCI).

The time to apply BWP activation according to the foregoingconfiguration switching indicator 4-15 for the BWP depends on thefollowing. The time to apply a configuration switch to the UE may dependon a predefined value (e.g., the configuration switch is applied after N(≥1) slots since receiving the configuration switching indicator), mayset by the base station for the UE via upper-layer signaling (e.g., RRCsignaling), or may be transmitted via the configuration switchingindicator 4-15. Further, the time to apply the configuration switch maybe determined by combining two or more of the above methods. Afterreceiving the configuration switching indicator 4-15 for the BWP, the UEmay apply a switched configuration from the time obtained by the abovemethod.

Hereinafter, a downlink control channel in a 5G communication systemwill be described in detail with reference to a drawing.

FIG. 5 illustrates an example of a control region (i.e., CORESET) inwhich a downlink control channel is transmitted in a 5G wirelesscommunication system according to an embodiment of the disclosure.

FIG. 5 shows an example in which a UE BWP 5-10 is configured on thefrequency axis and two control regions (control region #1 5-01 andcontrol region #2 5-02) are configured in one slot 5-20 on the timeaxis. Control region #1 5-01 and control region #2 5-02 may beconfigured in a particular frequency resource 5-03 in the entire UE BWP5-10 on the frequency axis. Each control region may be configured withone or a plurality of OFDM symbols on the time axis, which may bedefined as control region set duration 5-04.

Referring to FIG. 5, control region #1 5-01 is configured with a controlresource set duration of two symbols, and control region #2 5-02 isconfigured with a control resource set duration of one symbol.

The control region in 5G described above may be configured by the basestation for the UE through upper-layer signaling (e.g., systeminformation, an MIB, or RRC signaling). Configuring a control region forthe UE means that the base station provides the UE with information,such as the identity of the control region, a frequency position of thecontrol region, the symbol duration of the control region, or the like.For example, the configuration of a control region may include pieces ofinformation illustrated in Table 4.

TABLE 4 ControlResourceSet ::= SEQUENCE { --Corresponds to L1 parameter‘CORESET-ID’ controlResourceSetId , (Control region identity)frequencyDomainResources BIT STRING (SIZE (45)), (Frequency-domainresource allocation information) duration INTEGER(1..maxCoReSetDuration), (Time-domain resource allocation information)cce-REG-MappingType CHOICE { (CCE-to-REG mapping type) interleavedSEQUENCE { reg-Bundle Size ENUMERATED {n2, n3, n6}, (REG bundle size)precoderGranularity ENUMERATED {sameAsREG-bundle, allContiguousRBs},interleaverSize ENUMERATED {n2, n3, n6} (Interlever size) shiftindexINTEGER(0..maxNrofPhysicalResourceBlocks-1) OPTIONAL (Interlever shift)}, nonInterleaved NULL }, tci-StatesPDCCH SEQUENCE(SIZE (1..maxNrofTCI-StatesPDCCH)) OF TCI-StateId OPTIONAL, (QCL configuration information)tci-PresentInDCI ENUMERATED {enabled} OPTIONAL, -- Need S }

In Table 4, tci-StatesPDCCH (hereinafter, simply referred to as atransmission configuration indicator (TCI) state) configurationinformation may include information about the index of one or aplurality of synchronization signals (SSs)/physical broadcast channel(PBCH) blocks in a quasi co-located (QCL) relationship with ademodulation reference signal (DMRS) transmitted in the control regionor the index of a channel state information reference signal (CSI-RS).

Hereinafter, methods of allocating time and frequency resources for datatransmission in NR will be described.

NR provides the following specific frequency-domain resource allocations(FD-RAs) in addition to frequency-domain resource candidate allocationthrough a BWP indication illustrated above.

FIG. 6 illustrates three frequency-domain resource allocation methods oftype 0 6-00, type 1 6-05, and a dynamic switch 6-10 that may beconfigured through an upper layer in NR according to an embodiment ofthe disclosure.

Referring to FIG. 6, when a UE is configured to use only resource type 0through upper-layer signaling (6-00), some downlink control information(DCI) for allocating a PDSCH to the UE has a bitmap of N_(RBG) bits, acondition for which will be described later. Here, N_(RBG) denotes thenumber of resource block groups (RBGs) determined as in Table 4according to a BWP size allocated by a BWP indicator and a upper-layerparameter rbg-Size, and the RBG phase indicated by 1 by the bitmap, anddata is transmitted on an RBG indicated by 1 according to the bitmap.

TABLE 5 Configuration Configuration BWP Size 1 2  1-36 2 4 37-72 4 8 73-144 8 16 145-275 16 16

When the UE is configured to use only resource type 1 6-05 throughupper-layer signaling, some DCI for allocating a PDSCH to the UE hasfrequency-domain resource allocation information of ┌log₂(N_(RB)^(DL,BWP)(N_(RB) ^(DL,BWP)+¹)/2)┐ bits, a condition for which will bedescribed later. Through this information, the base station canconfigure a starting virtual resource block (VRB) 6-20 and the length6-25 of frequency-domain resources consecutively allocated therefrom.

When the UE is configured to use both resource type 0 and resource type1 through upper-layer signaling (6-10), some DCIs for allocating a PDSCHto the UE has frequency-domain resource allocation information of bitsof a greater value 6-35 among a payload 6-15 for configuring resourcetype 0 and payloads 6-20 and 6-25 for configuring resource type 1, acondition for which will be described later. Here, one bit 6-30 is addedto the most significant bit (MSB) of the frequency-domain resourceallocation information in the DCI, in which 0 indicates that resourcetype 0 is used, and 1 indicates that resource type 1 is used.

FIG. 7 illustrates an example of time-domain resource allocation in NRaccording to an embodiment of the disclosure.

Referring to FIG. 7, a base station can indicate a time-domain positionof a PDSCH resource allocated to a UE according to the start position7-00 and the length 7-05 of an OFDM symbol in a slot 7-10 dynamicallyindicated based on the subcarrier spacing (μ_(PDSCH), μ_(PDCCH)) of adata channel and a control channel configured via an upper layer, ascheduling offset (K₀) value, and DCI.

FIG. 8 illustrates an example of time-domain resource allocationaccording to the subcarrier spacing of a data channel and a controlchannel according to an embodiment of the disclosure.

Referring to FIG. 8, when a data channel and a control channel have thesame subcarrier spacing (8-00, μ_(PDSCH)=μ_(PDCCH)), since a data slotnumber and a control slot number are the same, a base station and a UErecognize that a scheduling offset occurs in accordance withpredetermined slot offset K₀. When the subcarrier spacing of the datachannel and the subcarrier spacing of the control channel are different(8-05, μ_(PDSCH)≠μ_(PDCCH)), since a data slot number and a control slotnumber are different, the base station and the UE recognize that ascheduling offset occurs in accordance with predetermined slot offset K₀based on the subcarrier spacing of the PDCCH.

In NR, for efficient control channel reception of a UE, various types ofDCI formats as shown in Table 6 are provided according to purposes.

TABLE 6 DCI format Usage 0_0 Scheduling of physical uplink sharedchannel (PUSCH) in one cell 0_1 Scheduling of PUSCH in one cell 1_0Scheduling of PDSCH in one cell 1_1 Scheduling of PDSCH in one cell 2_0Notifying a group of UEs of the slot format 2_1 Notifying a group of UEsof the PRB(s) and OFDM symbol(s) where UE may assume no transmission isintended for the UE 2_2 Transmission of TPC commands for physical uplinkcontrol channel (PUCCH) and PUSCH 2_3 Transmission of a group of TPCcommands for SRS transmissions by one or more UEs

For example, the base station may use DCI format 1_0 or DCI format 1_1to schedule a PDSCH for one cell.

DCI format 0_1 includes at least the following pieces of informationwhen transmitted together with a CRC scrambled with a cell radio networktemporary identifier (C-RNTI), a configured scheduling RNTI (CS-RNTI),or a new-RNTI.

-   -   Identifier for DCI formats (1 bit): DCI format indicator, which        is always set to 1.    -   Frequency domain resource assignment (N_(RBG) bits or        ┌log₂(N_(RB) ^(DL,BWP)(N_(RB) ^(DL,BWP)+¹)/2)┐ bits): Indicates        frequency-domain resource allocation. When DCI format 1_0 is        monitored in a UE-specific search space, N_(RB) ^(DL,BWP) is the        size of an active DL BWP; otherwise, N_(RB) ^(DL,BWP) is the        size of an initial DL BWP. N_(RBG) is the number of resource        block groups. A detailed method is illustrated in the foregoing        frequency-domain resource allocation.    -   Time domain resource assignment (0 to 4 bits): Indicates        time-domain resource allocation according to the foregoing        description.    -   VRB-to-PRB mapping (1 bit): 0 indicates non-interleaved        VRP-to-PRB mapping, and 1 indicates interleaved VRP-to-PRB        mapping.    -   Modulation and coding scheme (5 bits): Indicates a modulation        order and a coding rate used for PDSCH transmission.    -   New data indicator (1 bit): Indicates whether a PDSCH        corresponds to initial transmission or retransmission depending        on toggling.    -   Redundancy version (2 bits): Indicates a redundancy version used        for PDSCH transmission.    -   Hybrid automatic repeat request (HARQ) process number (4 bits):        Indicates an HARQ process number used for PDSCH transmission.    -   Downlink assignment index (DAI) (2 bits): DAI indicator.    -   Transmit power control (TPC) command for scheduled PUCCH (2        bits): PUCCH power control indicator.    -   PUCCH resource indicator (3 bits): PUCCH resource indicator,        which indicates one of eight resources configured via an upper        layer.    -   PDSCH-to-HARQ_feedback timing indicator (3 bits): HARQ feedback        timing indicator, which indicates one of eight feedback timing        offsets configured via an upper layer.

DCI format 1_1 includes at least the following pieces of informationwhen transmitted together with a CRC scrambled with a cell radio networktemporary identifier (C-RNTI), a configured scheduling RNTI (CS-RNTI),or a new-RNTI.

-   -   Identifier for DCI formats (1 bit): DCI format indicator, which        is always set to 1.    -   Carrier indicator (0 or 3 bits): Indicates a CC (or cell) in        which a PDSCH allocated by DCI is transmitted.    -   Bandwidth part indicator (0, 1, or 2 bits): Indicates a BWP in        which a PDSCH allocated by DCI is transmitted.    -   Frequency domain resource assignment (payload is determined        according to the foregoing frequency-domain resource        allocation): Indicates frequency-domain resource allocation.        N_(RB) ^(DL,BWP) is the size of an active DL BWP. A detailed        method is illustrated in the foregoing frequency-domain resource        allocation.    -   Time domain resource assignment (0 to 4 bits): Indicates        time-domain resource allocation according to the foregoing        description.    -   VRB-to-PRB mapping (0 or 1 bit): 0 indicates non-interleaved        VRP-to-PRB mapping, and 1 indicates interleaved VRP-to-PRB        mapping. When frequency-domain resource allocation is set to        resource type 0, this information is 0 bits.    -   PRB bundling size indicator (0 or 1 bit): When upper-layer        parameter prb-BundlingType is not set or is set to ‘static’,        this information is 0 bits; when upper-layer parameter        prb-BundlingType is set to ‘dynamic’, this information is 1 bit.    -   Rate matching indicator (0, 1, or 2 bits): Indicates a rate        matching pattern.    -   Zero power (ZP) CSI-RS trigger (0, 1, or 2 bits): Indicator        triggering an aperiodic ZP CSI-RS.    -   For transport block 1:        -   Modulation and coding scheme (5 bits): Indicates a            modulation order and a coding rate used for PDSCH            transmission.        -   New data indicator (1 bit): Indicates whether a PDSCH            corresponds to initial transmission or retransmission            depending on toggling.        -   Redundancy version (2 bits): Indicates a redundancy version            used for PDSCH transmission.    -   For transport block 2:        -   Modulation and coding scheme (5 bits): Indicates a            modulation order and a coding rate used for PDSCH            transmission.        -   New data indicator (1 bit): Indicates whether a PDSCH            corresponds to initial transmission or retransmission            depending on toggling.        -   Redundancy version (2 bits): Indicates a redundancy version            used for PDSCH transmission.    -   HARQ process number (4 bits): Indicates an HARQ process number        used for PDSCH transmission.    -   Downlink assignment index (0, 2, or 4 bits): DAI indicator.    -   TPC command for scheduled PUCCH (2 bits): PUCCH power control        indicator.    -   PUCCH resource indicator (3 bits): PUCCH resource indicator,        which indicates one of eight resources configured via an upper        layer.    -   PDSCH-to-HARQ_feedback timing indicator (3 bits): HARQ feedback        timing indicator, which indicates one of eight feedback timing        offsets configured via an upper layer.    -   Antenna port (4, 5, or 6 bits): Indicates a DMRS port and a code        divisional multiplexing (CDM) group without data.    -   Transmission configuration indication (0 or 3 bits): TCI        indicator.    -   Sounding reference signal (SRS) request (2 or 3 bits): SRS        transmission request indicator.    -   Code block group (CBG) transmission information (0, 2, 4, 6, or        8 bits): Indicator indicating whether code block groups in an        allocated PDSCH are transmitted. 0 indicates that the CBGs are        not transmitted, and 1 indicates that the CBGs are transmitted.    -   CBG flushing-out information (0 or 1 bit): Indicator indicating        whether previous CBGs are contaminated. 0 indicates that the        CBGs may be contaminated, and 1 indicates that the CBGs may be        combinable in retransmission reception.    -   DMRS sequence initialization (0 or 1 bit): DMRS scrambling ID        selection indicator.

The number of pieces of DCI having different sizes that a UE can receiveper slot in a cell is up to 4. The number of pieces of DCI havingdifferent sizes scrambled with a C-RNTI that a UE can receive per slotin a cell is up to 3.

FIG. 9 illustrates the wireless protocol structures of a base stationand a UE when single cell 9-00, carrier aggregation (CA) 9-10, dualconnectivity (DC) 9-20 are performed according to an embodiment of thedisclosure.

Referring to FIG. 9, a wireless protocol of a next-generation mobilecommunication system includes NR service data adaptation protocols(SDAPs) 9-25 and 9-70, NR packet data convergence protocols (PDCPs) 9-30and 9-65, NR radio link controls (RLCs) 9-35 and 9-60, and NR mediumaccess controls (MACs) 9-40 and 9-55 respectively at a UE and an NR basestation.

Main functions of the NR SDAPs 9-25 and 9-70 may include some of thefollowing functions.

-   -   Transfer of user plane data    -   Mapping between QoS flow and DRB for both DL and UL    -   Marking QoS flow ID in both DL and UL packets    -   Reflective QoS flow-to-DRB mapping for UL SDAP PDUs

Regarding the SDAP-layer devices, the UE may receive a configurationabout whether to use a header of the SDAP-layer devices or whether touse a function of the SDAP-layer devices for each PDCP-layer device,each bearer, or each logical channel via an RRC message. When an SDAPheader is configured, a one-bit NAS QoS reflective indicator (NASreflective QoS) and a one-bit AS QoS reflective indicator (AS reflectiveQoS) of the SDAP header may be used for indication to enable the UE toupdate or reconfigure uplink and downlink QoS flows and mappinginformation for a data bearer. The SDAP header may include QoS flow IDinformation indicating QoS. The QoS information may be used as a dataprocessing priority, scheduling information, and the like in order tosupport a desired service.

Main functions of the NR PDCPs 9-30 and 9-65 may include some of thefollowing functions.

-   -   Header compression and decompression (ROHC only)    -   Transfer of user data    -   In-sequence delivery of upper-layer PDUs    -   Out-of-sequence delivery of upper-layer PDUs    -   PDCP PDU reordering for reception    -   Duplicate detection of lower-layer SDUs    -   Retransmission of PDCP SDUs    -   Ciphering and deciphering    -   Timer-based SDU discard in uplink.

Among the above functions, the reordering function of the NR PDCPdevices refers to a function of rearranging PDCP PDUs received in alower layer in order based on the PDCP sequence number (SN) and mayinclude a function of transmitting the data to an upper layer in theorder of rearrangement or a function of immediately transmitting thedata regardless of order. In addition, the reordering function mayinclude a function of recording lost PDCP PDUs via reordering, mayinclude a function of reporting the state of lost PDCP PDUs to atransmitter, and may include a function of requesting retransmission oflost PDCP PDUs.

Main functions of the NR RLCs 9-35 and 9-60 may include some of thefollowing functions.

-   -   Transfer of upper-layer PDUs    -   In-sequence delivery of upper-layer PDUs    -   Out-of-sequence delivery of upper-layer PDUs    -   Error Correction through ARQ    -   Concatenation, segmentation, and reassembly of RLC SDUs    -   Re-segmentation of RLC data PDUs    -   Reordering of RLC data PDUs    -   Duplicate detection    -   Protocol error detection    -   RLC SDU discard    -   RLC re-establishment

Among the above functions, the in-sequence delivery function of the NRRLC devices refers to a function of delivering RLC SDUs received from alower layer to an upper layer in order, and may include a function ofreassembling and delivering a plurality of RLC SDUs when one originalRLC SDU is divided into the plurality of RLC SDUs to be received.Further, the in-sequence delivery function may include a function ofrearranging received RLC PDUs based on the RLC SN or the PDCP SN and mayinclude a function of recording lost RLC PDUs via reordering. Inaddition, the in-sequence delivery function may include a function ofreporting the state of lost RLC PDUs to a transmitter, may include afunction of requesting retransmission of lost RLC PDUs, and, if there isa lost RLC SDU, may include a function of delivering only RLC SDUsbefore the lost RLC SDU to an upper layer in order. Furthermore, thein-sequence delivery function may include a function of delivering allRLC SDUs, received before a timer starts, to an upper layer in orderwhen the timer has expired despite the presence of a lost RLC SDU, ormay include a function of delivering all RLC SDUs received so far to anupper layer in order when the timer expires despite the presence of alost RLC SDU. Further, the NR RLC devices may process RLC PDUs in orderof reception (the order of arrival regardless of the order of SNs) andmay deliver the RLC PDUs to the PDCP devices in an out-of-sequencemanner. For a segment, the NR RLC devices may receive segments that arestored in a buffer or are to be received later, may reconstruct thesegment into one whole RLC PDU, may process the RLC PDU, and may deliverthe RLC PDU to the PDCP devices. The NR RLC layers may not include aconcatenation function, and the concatenation function may be performedin the NR MAC layers or may be replaced with a multiplexing function ofthe NR MAC layers.

The out-of-sequence delivery function of the NR RLC devices refers to afunction of delivering RLC SDUs received from a lower layer directly toan upper layer regardless of order, and may include a function ofreassembling and delivering a plurality of RLC SDUs when one originalRLC SDU is divided into the plurality of RLC SDUs to be received. Inaddition, the out-of-sequence delivery function may include a functionof recording lost RLC PDUs by storing and reordering the RLC SNs or PDCPSNs of received RLC PDUs.

The NR MACs 9-40 and 9-55 may be connected to a plurality of NRRLC-layer devices configured in one device, and main functions of the NRMACs may include some of the following functions.

-   -   Mapping between logical channels and transport channels    -   Multiplexing/demultiplexing of MAC SDUs    -   Scheduling information reporting    -   Error correction through HARQ    -   Priority handling between logical channels of one UE    -   Priority handling between UEs by means of dynamic scheduling    -   MBMS service identification    -   Transport format selection    -   Padding

NR PHY layers 9-45 and 9-50 may perform channel coding and modulation ofupper-layer data and convert the data into OFDM symbols to transmit theOFDM symbols via a wireless channel, or demodulate OFDM symbols receivedvia a wireless channel and perform channel decoding of the OFDM symbolsto deliver the OFDM symbols to an upper layer.

Details of the wireless protocol structures may be changed variouslyaccording to a carrier (or cell) operating method. For example, when thebase station transmits data to the UE based on a single carrier (orcell), the base station and the UE use a protocol structure having eachlayer with a single structure as in 9-00. When the base stationtransmits data to the UE based on carrier aggregation (CA) usingmultiple carriers at a single TRP, the base station and the UE use aprotocol structure in which up to an RLC has a single structure but PHYlayers are multiplexed through a MAC layer as in 9-10. In anotherexample, when the base station transmits data to the UE based onconnectivity (DC) using multiple carriers at a plurality of TRPs, thebase station and the UE use a protocol structure in which up to an RLChas a single structure but PHY layers are multiplexed through MAC layersas in 9-20.

Referring to details of PDSCH transmission/reception procedures, such asthe DCI structures, the PDSCH time/frequency resource allocation, andthe wireless protocol structures described above, an NR system ofRelease 15 focuses on allocation of a PDSCH transmitted from a singletransmission point. Thus, in coordinated communication in which one UEreceives PDSCHs transmitted from a plurality of points, it is requiredto support an additional standard. For example, in current NR, when twoor more PDSCHs are scheduled for a UE in the same transmission band andoverlapping time periods, the UE is not forced to decode all of thePDSCHs (except in a special case where a PDSCH for transmitting a systeminformation block (SIB) is included or the like). Further, in currentNR, when two or more PDSCHs are scheduled in overlapping time periods,the UE assumes that the PDSCHs may have different priorities. Therefore,in this case, a particular UE may operate to decode only a PDSCH havinga high priority. However, in coordinated communication, since a UE needsto decode all PDSCHs transmitted from a plurality of points, an existingstandard related to PDSCH priority needs to be extended. In addition,the UE requires a high-performance receiver for PDSCH reception from aplurality of TRPs and involves high UE complexity in order to supportcoordinated communication. Therefore, there is a need for a method forreducing UE complexity for supporting coordinated communication.

The disclosure illustrates embodiments of improving efficiency incoordinated communication by providing a PDSCH prioritizing method and amethod for reducing UE reception complexity in view of coordinatedcommunication.

The following details are applicable to frequency division duplex (FDD)and time division duplex (TDD) systems.

In the following disclosure, upper-layer signaling is a method of signaltransmission from a base station to a UE using a downlink data channelof a physical layer or from a UE to a base station using an uplink datachannel of a physical layer and may also be referred to as RRCsignaling, PDCP signaling, or an MAC control element (CE).

In the following disclosure, in determining whether coordinatedcommunication is applied, a UE can use various methods, such as allowinga PDCCH(s) for allocating a PDSCH to which coordinated communication isapplied to have a specific format, allowing a PDCCH(s) for allocating aPDSCH to which coordinated communication is applied to include aspecific indicator indicating whether communication is applied,scrambling a PDCCH(s) for allocating a PDSCH to which coordinatedcommunication is applied with a specific RNTI, or assuming thatcoordinated communication is applied in a specific period indicated viaan upper layer. Hereinafter, for convenience of description, a UEreceiving a PDSCH to which coordinated communication is applied based onconditions similar to the above is referred to as a non-coherent jointtransmission (NC-JT) case.

In the following disclosure, prioritizing A and B may be construed invarious ways, for example, as selecting a higher priority according to apredetermined priority rule to perform an operation correspondingthereto or as omitting, skipping, or dropping an operation correspondingto a lower priority.

In the following disclosure, examples of the above will be describedwith reference to a plurality of embodiments, which may not beindependent, and it is possible to apply one or more embodimentssimultaneously or in combination.

First Embodiment: Multiple DCI Reception for NC-JT

Unlike conventional systems, a 5G wireless communication system cansupport not only services requiring a high transmission rate but alsoservices having a very short transmission delay and services requiring ahigh connection density. In a wireless communication network including aplurality of cells, TRPs, or beams, coordinated transmission betweencells, TRPs, and/or beams is one elementary technique for satisfying theforegoing various service requirements by increasing the strength of asignal received by a UE or efficiently controlling interference betweencells, TRPs, and/or beams.

Joint transmission (JT) is a representative transmission technique forcoordinated communication and supports one UE through different cells,TRPs, or/and beams, thus increasing the strength of a signal received bythe UE. Since channels between a UE and individual cells, TRPs, or/andbeams may have significantly different characteristics, different typesof precoding, modulation and coding schemes (MCSs), resource allocation,and the like need to be applied to links between the UE and theindividual cells, TRPs, or/and beams. Particularly, in non-coherentjoint transmission (NC-JT), which supports non-coherent precoding foreach cell, TRP, or/and beam, it is important to configure individual DLtransmission information for each cell, TRP, or/and beam. Theconfiguration of the individual DL transmission information for eachcell, TRP, or/and beam is a major factor to increase payload necessaryfor DL DCI transmission, which may adversely affect the receptionperformance of a PDCCH for transmitting the DCI. Therefore, it isnecessary to carefully design a tradeoff between the amount of DCI andthe reception performance of a PDCCH in order to support JT.

FIG. 10 illustrates examples of radio resource allocation per TRPaccording to a JT technique and a situation according to an embodimentof the disclosure.

Referring to FIG. 10, 10-00 illustrates coherent joint transmission(C-JT) supporting coherent precoding between individual cells, TRPs,or/and beams. In C-JT, TRP A 10-05 and TRP B 10-10 transmit the samedata (or PDSCH) to a UE 10-15, and a plurality of TRPs performs jointprecoding, which means that TRP A 10-05 and TRP B 10-10 transmit thesame DMRS ports (e.g., both TRPs transmit DMRS ports A and B) forreceiving the same PDSCH. In this case, the UE 10-15 receives one pieceof DCI for receiving one PDSCH demodulated by DMRS ports A and B.

Referring to FIG. 10, 10-20 illustrates non-coherent joint transmission(NC-JT) supporting non-coherent precoding between individual cells,TRPs, or/and beams. In NC-JT, the individual cells, TRPs, or/and beamstransmit different data (or PDSCHs), and individual precoding may beapplied to each data (or PDSCH), which means that TRP A 10-25 and TRP B10-30 transmit different DMRS ports (e.g., TRP A transmits DMRS port Aand TRP B transmits DMRS port B) for receiving the different PDSCHs to aUE 10-35. In this case, the UE 10-35 receives two types of DCI forreceiving PDSCH A demodulated by DMRS port A and PDSCH B demodulated byDMRS port B.

For example, in NC-JT, as illustrated at the bottom of FIG. 10, variousradio resource allocations may be considered, such as where the samefrequency and time resources are used by a plurality of TRPs (10-40),where frequency and time resources used by a plurality of TRPs neveroverlap (10-45), and where frequency and time resources used by aplurality of TRPs partially overlap (10-50). Particularly, in the caseof 10-50, DCI payload necessary for resource allocation informationlinearly increases according to the number of TRPs. This increase in DLDCI payload may adversely affect the reception performance of a PDCCHfor transmitting DCI or may, as described above, significantly increasethe DCI blind decoding complexity of a UE. Therefore, the disclosureprovides a PDSCH time and frequency resource allocation method forefficiently supporting NC-JT.

For supporting NC-JT, pieces of DCIs in various forms, structures, andrelationships may be considered to simultaneously allocate a pluralityof PDSCHs to one UE.

FIG. 11 illustrates four examples of a DCI design for supporting NC-JTaccording to an embodiment of the disclosure.

Referring to FIG. 11, in Case #1 11-00, N−1 different PDSCHs aretransmitted in N−1 additional TRPs (TRP #1 to TRP # N−1) other than aserving TRP (TRP #0) used when transmitting a single PDSCH. Case #111-00 illustrates an example in which control information about thePDSCHs transmitted in the additional TRPs is transmitted in the same DCIformat as that of control information about the PDSCH transmitted in theserving TRP. That is, a UE obtains the control information about thePDSCHs transmitted in the different TRPs (TRP #0 to TRP # N−1) throughpieces of DCIs (i.e., DCI #0 to DCI # N−1) having the same DCI formatand the same payload. In Case #1, the degree of freedom of each PDSCHcontrol (allocation) is completely guaranteed, while receptionperformance may be degraded due to a difference in coverage per DCI whenthe respective pieces of DCI are transmitted in the different TRPs.

Referring to FIG. 11, in Case #2 11-05, N−1 different PDSCHs aretransmitted in N−1 additional TRPs (TRP #1 to TRP # N−1) other than aserving TRP (TRP #0) used when transmitting a single PDSCH. Case #211-05 illustrates an example in which control information about thePDSCHs transmitted in the additional TRPs is transmitted in a differentform (different DCI format or different DCI payload) from that ofcontrol information about the PDSCH transmitted in the serving TRP. Forexample, DCI #0 transmitting the control information about the PDSCHtransmitted in the serving TRP (TRP #0) may include all informationelements of DCI format 1_0 or DCI format 1_1, while pieces of shortenedDCI (sDCI #0 to sDCI # N−2) transmitting the control information aboutthe PDSCHs transmitted in the cooperative TRPs (TRP #1 to TRP # N−1) mayinclude some of the information elements of DCI format 1_0 or DCI format1_1. Therefore, the pieces of sDCI transmitting the control informationabout the PDSCHs transmitted in the cooperative TRPs may have a smallerpayload than the normal DCI (nDCI) transmitting the control informationabout the PDSCH transmitted in the serving TRP or can include as manyreserved bits as the number of bits short of that of the nDCI. In Case#2, the degree of freedom of each PDSCH control (allocation) may berestricted depending on the content of an information element includedin sDCI, while the reception performance of sDCI may be improvedcompared to that of the nDCI and thus difference in coverage per DCI isless likely to occur.

Referring to FIG. 11, in Case #3 11-10, N−1 different PDSCHs aretransmitted in N−1 additional TRPs (TRP #1 to TRP # N−1) other than aserving TRP (TRP #0) used when transmitting a single PDSCH. Case #311-10 illustrates another example in which control information about thePDSCHs transmitted in the additional TRPs is transmitted in a differentform (different DCI format or different DCI payload) from that ofcontrol information about the PDSCH transmitted in the serving TRP. Forexample, DCI #0 transmitting the control information about the PDSCHtransmitted in the serving TRP (TRP #0) may include all informationelements of DCI format 1_0 or DCI format 1_1, while the controlinformation about the PDSCHs transmitted in the cooperative TRPs (TRP #1to TRP # N−1) can be transmitted by collecting only some of theinformation elements of DCI format 1_0 or DCI format 1_1 in one piece ofsecondary DCI (sDCI). For example, the sDCI may include at least one ofpieces of HARQ-related information, such as a frequency-domain resourceassignment, a time-domain resource assignment, and an MCS of thecooperative TRPs. In addition, for information not included in the sDCI,such as a BWP indicator or a carrier indicator, it is possible to followthat in the DCI (DCI #0, normal DCI, or nDCI) of serving TRP. In Case#3, the degree of freedom of each PDSCH control (allocation) may berestricted depending on the content of an information element includedin sDCI, while it is possible to adjust the reception performance of thesDCI and the DCI blind decoding complexity of a UE is lower than in Case#1 or #2.

Referring to FIG. 11, in Case #4 11-15, N−1 different PDSCHs aretransmitted in N−1 additional TRPs (TRP #1 to TRP # N−1) other than aserving TRP (TRP #0) used when transmitting a single PDSCH. Case #411-15 illustrates an example in which control information about thePDSCHs transmitted in the additional TRPs is transmitted in the same DCI(long DCI: lDCI) as that for control information about the PDSCHtransmitted in the serving TRP. That is, a UE obtains the controlinformation about the PDSCHs transmitted in the different TRPs (TRP #0to TRP # N−1) through the single DCI. In Case #4, the DCI blind decodingcomplexity of a UE is not increased, while the degree of freedom ofPDSCH control (allocation) is low, for example, the number ofcooperative TRPs is limited according to restriction of long DCIpayload.

In the following description and embodiments, sDCI may refer to variouspieces of auxiliary DCI, such as shortened DCI, secondary DCI, or normalDCI (DCI format 1_0 or 1_1 described above) including PDSCH controlinformation transmitted in a cooperative TRP. Further, unlessspecifically restricted, the foregoing description may be similarlyapplied to these various pieces of auxiliary DCI.

In the following description and embodiments, Case #1 11-00, Case #211-05, and Case #3 11-10, in which one or more pieces of DCI (PDCCHs)are used for supporting NC-JT, are classified as multiple PDCCH-basedNC-JT, and Case #4 11-15, in which a single piece of DCI (PDCCH) is usedfor supporting NC-JT, is classified as single PDCCH-based NC-JT.

In the following description and embodiments, there are provided a PDSCHprioritizing method considering multiple PDCCH-based NC-JT and singlePDCCH-based NC-JT and a method for reducing UE complexity for NC-JT.

In embodiments, when actually applied, a “cooperative TRP” may bereplaced with various terms, such as a “cooperative panel” or“cooperative beam”.

In embodiments, although “when NC-JT is applied” may be interpreted invarious ways depending on the situation, such as “when a UEsimultaneously receives one or more PDSCHs in one BWP”, “when a UEsimultaneously receives two or more TCI indications in one BWP”, or“when a PDSCH received by a UE is associated with one or more DMRS portgroups”, one expression is used for convenience of description.

In the disclosure, various wireless protocol structures may be used forNC-JT according to a TRP deployment scenario. For example, when there isno backhaul delay between cooperative TRPs or there is a short backhauldelay therebetween, it is possible to use a MAC layer multiplexing-basedstructure similar to that in 9-10 of FIG. 9 (i.e., a CA-like method).However, when a backhaul delay between cooperative TRPs is too long tobe not negligible (e.g., when a time of 2 ms or longer is required for aCSI exchange or a scheduling information exchange between cooperativeTRPs), it is possible to use a structure in which TRPs are independentfrom an RLC layer, which is similar to that in 9-20 of FIG. 9, thussecuring robustness to a delay (i.e., a DC-like method).

Second Embodiment: Method for Prioritizing PDSCHs

This embodiment provides a specific method for prioritizing PDSCHs whentwo or more PDSCHs are scheduled in the same transmission band, forexample, the same transmission band, the same component carrier, or thesame BWP, and the overlapping time resource as described in the firstembodiment.

FIG. 12 illustrates the priorities of PDSCHs in current NR and thepriorities of PDSCHs according to an embodiment of the disclosure.

Referring to FIG. 12, in current NR, when two or more PDSCHs arescheduled for a UE in the same transmission band and overlapping timeperiods, the UE is not forced to decode all of the PDSCHs (except in aspecial case where a PDSCH for transmitting an SIB is included or thelike). Further, in current NR, when two PDSCHs are scheduled inoverlapping time periods, the UE assumes that the PDSCHs may havedifferent priorities. Specifically, pieces of schedule information aboutthe two PDSCHs are reported to the UE via DCI or a semi-static method(12-05 and 12-10), in which a PDSCH 12-15 scheduled by DCU 2 (i.e.,12-10) reported later in order of time is assumed to have a higherpriority than a PDSCH 12-20 scheduled by DCI 1 (i.e., 12-05) reportedearlier in order of time (12-01). Here, the UE may operate in variousways, for example, may decode only the PDSCH having the higher priorityor may decode both the PDSCH having the higher priority and the PDSCHhaving the lower priority, depending on implementation.

However, when NC-JT is used, a UE and a base station expect all PDSCHsscheduled in a specific time resource to be decoded, and thus it isnecessary in NR to change PDSCH priorities described above. Properlydesigning a PDSCH priority ensures that a UE decodes all PDSCHs forNC-JT and enables the UE to essentially decode only a PDSCH having ahigh priority among the other PDSCHs and to autonomously determinewhether to decode a PDSCH having a low priority, thus reducing UEcomplexity.

The following principles may be considered for prioritization. I) WhenPDSCHs scheduled in overlapping time resources by different pieces ofDCI 12-25 and 12-30 are PDSCHs 12-35 and 12-40 for NC-JT, these PDSCHsneed to have the same priority so that a UE decodes all of the PDSCHs(12-21). II) When PDSCHs scheduled in overlapping time resources bydifferent pieces of DCI 12-05 and 12-10 are PDSCHs 12-15 and 12-20 notfor NC-JT, different priorities may be applied to these PDSCHs. To applythese principles, it is necessary to distinguish a PDSCH for NC-JT and aPDSCH not for NC-JT. To this end, the following examples may beconsidered.

A. Time difference (K₀) between PDSCHs scheduled in overlapping timeresources and schedule information notification times of PDSCHs: When aplurality of PDSCHs is scheduled in overlapping time resources, the UEcan distinguish whether each PDSCH is for NC-JT through the K₀ value ofeach PDSCH. For example, the UE may determine that PDSCHs having thesame K₀ value are PDSCHs for NC-JT and may determine that PDSCHs havingdifferent K₀ values are PDSCHs not for NC-JT. This example may be usefulwhen the backhaul transmission delay times of respective transmissionpoints are similar or predictable so that the schedule informationnotification times or K₀ values of PDSCHs may be equally matched. Inanother example, the UE may determine that PDSCHs between which thedifference in K₀ value is within a certain value (|x−y| is within acertain value in FIG. 12) are PDSCHs for NC-JT and may determine thatthe other PDSCHs are PDSCHs not for NC-JT. This example may be usefulwhen it is difficult to match the schedule information notificationtimes or the K₀ values of PDSCHs due to different backhaul delay timesof respective transmission points.

B. TCI information about PDSCHs scheduled in overlapping time resources:When a plurality of PDSCHs is scheduled in overlapping time resources,if a TCI indicator is included in PDSCH scheduling information, such asDCI, the UE can distinguish whether each PDSCH is for NC-JT through acorresponding TCI indicator. For example, the UE may determine thatPDSCHs having different TCI indicators are PDSCHs for NC-JT and maydetermine that PDSCHs having the same TCI indicator are PDSCHs not forNC-JT. This example may be useful when transmission/reception beams forrespective transmission points are different or channel characteristicsare significantly different.

C. Antenna port or DMRS CDM group information about PDSCHs scheduled inoverlapping time resources: When a plurality of PDSCHs is scheduled inoverlapping time resources, the UE can distinguish whether each PDSCH isfor NC-JT through the antenna port or DMRS CDM group allocation of thePDSCH. For example, the UE may determine that PDSCHs having allocatedantenna ports or DMRS CDM groups which do not overlap are PDSCHs forNC-JT and may determine that PDSCHs having allocated antenna ports orDMRS CDM groups, at least one of which overlaps, are PDSCHs not forNC-JT. This example may be useful when data transmitted from respectivetransmission points are received by the UE via different layers.

D. HARQ process information about PDSCHs scheduled in overlapping timeresources: When a plurality of PDSCHs is scheduled in overlapping timeresources, the UE can distinguish whether each PDSCH is for NC-JTthrough an HARQ process number allocated to the PDSCH. For example, theUE may determine that PDSCHs having the same HARQ process number arePDSCHs for NC-JT and may determine that PDSCHs having different HARQprocess numbers are PDSCHs not for NC-JT. This example may be usefulwhen retransmission of all data transmitted via NC-JT is managed in oneHARQ process.

E. RNTI information associated with PDSCHs scheduled in overlapping timeresources: When a plurality of PDSCHs is scheduled in overlapping timeresources, the UE can distinguish whether each PDSCH is for NC-JTthrough an RNTI scrambling schedule information about the PDSCH. Forexample, there may be an RNTI not used for NC-JT, and there may be anRNTI used only for NC-JT. The RNTI not used for NC-JT may be an RNTIused for semi-persistent scheduling.

Examples A to E are not mutually exclusive, and two or more examples maybe used in combination. For example, using example A and B at the sametime, only a PDSCH satisfying the conditions specified in both examplesmay be determined as a PDSCH for NC-JT. Although various othercombinations are possible, not all possibilities are listed in order notto obscure the subject matter of the description. In addition to theabove examples, similar methods for distinguishing a PDSCH for NC-JT maybe used.

When a PDSCH for NC-JT is distinguished, the UE and the base station mayset the same priority for PDSCHs for NC-JT and may set differentpriorities for respective PDSCHs not for NC-JT. Further, when PDSCHs forNC-JT and PDSCHs not for NC-JT are mixed, different priorities may beset for PDSCHs 12-60 and 12-65 for NC-JT scheduled by pieces of DCI12-45 and 12-55 and a PDSCH 12-70 not for NC-JT scheduled by another DCI12-50 (12-41). When a plurality of PDSCHs having the same priority isscheduled in overlapping time resources, the UE needs to decode all ofthe PDSCHs. However, when a plurality of PDSCHs having differentpriorities is scheduled, the UE essentially needs to decode a PDSCHhaving the highest priority. When the UE is incapable of decoding aplurality of PDSCHs scheduled in overlapping time resources, the basestation may not schedule PDSCHs having the same priority.

The following examples may be considered as a method for determining thepriority of a PDSCH not for NC-JT.

1) The UE and the base station may set different priorities according toPDSCH schedule information notification time. For example, a PDSCHhaving a later PDSCH schedule information notification time or a smallerK₀ value may have a higher priority than a PDSCH in the opposite case.When PDSCHs for NC-JT and not for NC-JT are mixed, the UE and the basestation may use the minimum value among the K₀ values of the PDSCHs todetermine the priority of a PDSCH for NC-JT.

2) The UE and the base station may set different priorities according towhether a PDSCH is a PDSCH for NC-JT. For example, when PDSCHs for NC-JTand not for NC-JT are mixed, a PDSCH for NC-JT may have a higherpriority than a PDSCH not for NC-JT.

3) The UE and the base station may set different priorities according tothe scheme in which a PDSCH is scheduled. For example, a dynamicallyscheduled PDSCH via DCI or the like, may have a higher priority than asemi-persistently scheduled PDSCH, that is, a PDSCH scheduled accordingto a specified cycle configured via RRC.

4) The UE and the base station may set different priorities according towhether a PDSCH is repeatedly transmitted. For example, when one PDSCHis repeated during a plurality of slots while another PDSCH is notrepeated, the PDSCH not repeated may have a higher priority.

Two or more of the above examples may be implement in combination asnecessary, and similar methods for determining the priority of a PDSCHmay be used in addition to the above examples. Further, when the aboveexamples are implemented in combination, the priorities of therespective methods may be hierarchically configured. For example, PDSCHsmay be prioritized first according to Method 3, followed byprioritization by Method 4 if there are PDSCHs having the same priority,followed by prioritization by Method 1 if there are still PDSCHs havingthe same priority, and then followed by prioritization by Method 2 ifthere are PDSCHs having the same priority. Although the order of theprioritization methods may be changed, not all possibilities are listedin order not to obscure the subject matter of the description.

The methods for prioritizing PDSCHs scheduled in overlapping timeresources according to the embodiment may be summarized as in aflowchart illustrated in FIG. 13.

FIG. 13 is a flowchart illustrating a method for prioritizing PDSCHsscheduled in overlapping time resources according to an embodiment ofthe disclosure.

Referring to FIG. 13, a UE determines the number of PDSCHs allocated onan OFDM symbol (13-10). When the number of PDSCHs is 1, the UE receivesthe PDSCH (13-20). When the number of PDSCHs exceeds 1, the UEdetermines whether an NC-JT PDSCH is included in the PDSCHs (13-30), inwhich at least one or more of the foregoing methods in Examples A to Emay be used. Subsequently, the UE assigns a priority value to each PDSCH(13-40), in which one or more of the foregoing methods in Examples 1) to4) may be used. When an NC-JT PDSCH is included (13-50), the samepriority value is assigned for NC-JT PDSCHs (13-60), in which thepriority value of the NC-JT PDSCHs may be different from that of anon-NC-JT PDSCH. When the NC-JT PDSCHs have the highest priority(13-65), the UE receives the NC-JT PDSCHs (13-80); otherwise, the UEreceives a PDSCH assigned the highest priority (13-90). When no NC-JTPDSCH is included (13-50), the UE assigns different priority values toall PDSCHs (13-70) and receives a PDSCH with the highest priority(13-90).

Third Embodiment: Method for Reducing Complexity of NC-JT Supporting UE

This embodiment provides various specific methods for reducing thereception complexity of an NC-JT supporting UE.

First, in multi-PDCCH-based NC-JT, a DMRS of a specific PDSCH for NC-JTmay overlap with another PDSCH for NC-JT on a frequency-time resource.In this case, decoding performance through the DMRS is degraded due tointerference by the overlapping PDSCH, and high UE reception complexityis required to overcome such degradation. In one method for reducing thereception complexity of an NC-JT supporting UE, a DMRS of a PDSCH forNC-JT may be configured so as not to overlap with another PDSCH forNC-JT on a frequency-time resource. To this end, the following examplesmay be considered.

a. When PDSCHs transmitted in multi-PDCCH-based NC-JT overlap onfrequency-time resources, a base station may configure the startpositions of DMRSs for the PDSCHs on a time resource, the lengths ofDMRS front-loaded symbols, DMRS types, the numbers of additional DMRSsymbols, and the positions of the additional DMRS symbols to be matched.Further, the base station may configure CDM groups or DMRS ports ofDMRSs of respective PDSCHs for NC-JT not to overlap.

Accordingly, the base station and the UE can avoid a DMRS of a PDSCH forNC-JT from overlapping with a DMRS or data of another PDSCH for NC-JT.The UE does not expect a case where a DMRS configuration for each PDSCHfor NC-JT is different from the above configuration, that is, a casewhere a DMRS of a specific PDSCH is configured to overlap with a DMRS ordata of another PDSCH, thereby reducing the reception complexity of theUE.

One example of the above configuration to avoid overlapping is asfollows.

-   -   The base station and the UE may share RRC configurations for        DMRSs for PDSCH mapping type A and mapping type B for all PDSCHs        for NC-JT, for example, DMRS-type or maxLength (the maximum        number of DMRS starting symbols), and this configuration may be        included in PDSCH-Config, dmrs-DownlinkForPDSCH-MappingTypeA,        dmrs-DownlinkForPDSCH-MappingTypeB, or DMRS-DownlinkConfig in        NR.    -   Even though PDSCH mapping types indicated by pieces of DCI for        respective PDSCHs are the same and both the offsets and the        lengths of PDSCH-allocated symbols are the same or one or more        thereof are different, the base station and the UE may configure        start symbols at which DMRSs of different PDSCHs are positioned        or additional symbols to have the same position or not to        overlap with data of a different PDSCH.    -   The base station and the UE may configure the same number of        DMRS front-load symbols and the same number of DMRS CDM groups        without data associated with an antenna port configuration        indicated by DCI for each PDSCH and may configure a different        CDM group for each antenna port.

For example, when DMRS-type=1 and the maximum number of DMRS startsymbols=2, limited DMRS port combinations in Table 7 including some ofthe antenna port configuration values available in NR can be used forNC-JT. For example, the following details may apply.

-   -   When two PDSCHs are scheduled for NC-JT and codepoints for the        DMRS ports of these PDSCHs are 7 and 8, respectively, the        numbers of front-load symbols of the DMRSs and the numbers of        DMRS CDM groups without data are the same and the DMRS CDM        groups are different. Thus, the DMRS ports are a DMRS port        combination of that can be allocated.    -   When two PDSCHs are scheduled for NC-JT and codepoints for the        DMRS ports of these PDSCHs are 12 and 13, respectively, the        numbers of front-load symbols of the DMRSs and the numbers of        DMRS CDM groups without data are the same and the DMRS CDM        groups are the same. Thus, the DMRS ports are a DMRS port        combination of that cannot be allocated.

Although there are various other combinations that can beallocated/cannot be allocated, not all possibilities are listed in ordernot to obscure the subject matter of the description. It is alsopossible to redefine DMRS port combinations allocable for NC-JT andcodepoints therefor.

TABLE 7 One Codeword: Codeword 0 enabled, Codeword 1 disabled Number ofDMRS CDM group(s) without DMRS Number of front- Value data port(s) loadsymbols 0 1 0 1 1 1 1 1 2 1 0, 1 1 3 2 0 1 4 2 1 1 5 2 2 1 6 2 3 1 7 20, 1 1 8 2 2, 3 1 9 2 0-2 1 10 2 0-3 1 11 2 0, 2 1 12 2 0 2 13 2 1 2 142 2 2 15 2 3 2 16 2 4 2 17 2 5 2 18 2 6 2 19 2 7 2 20 2 0, 1 2 21 2 2, 32 22 2 4, 5 2 23 2 6, 7 2 24 2 0, 4 2 25 2 2, 6 2 26 2 0, 1, 4 2 27 2 2,3, 6 2 28 2 0, 1, 4, 5 2 29 2 2, 3, 6, 7 2 30 2 0, 2, 4, 6 2 31 ReservedReserved Reserved

Although there may be other configurations to prevent overlappingbetween a DMRS of a PDSCH for NC-JT and another PDSCH for NC-JT, not allpossibilities are listed in order not to obscure the subject matter ofthe description.

b. When PDSCHs transmitted in multi-PDCCH-based NC-JT overlap onfrequency-time resources, rate matching may be indicated so that data ofa specific PDSCH prevents overlapping with a DMRS of another PDSCH. Forexample, the base station may semi-statically configure a rate matchingpattern including a DMRS symbol position of the other PDSCH and maydynamically activate the pattern by indicating the pattern to the UE viaDCI in NC-JT. Alternatively, the base station may configure ZP-CSI-RSsto include the DMRS symbol position of the other PDSCH and may apply theZP-CSI-RSs by indicating the ZP-CSI-RSs semi-statically or dynamicallyvia DCI.

Although there may be various methods similar to the above examples, notall possibilities are listed in order not to obscure the subject matterof the description.

For an NC-JT supporting UE to simultaneously support NC-JT and MU-MIMO,both interference cancellation between a plurality of PDSCHs transmittedvia NC-JT or codewords and MU interference cancellation are needed, andthus very high receiver complexity is required. NC-JT is effective whenthere is a transmission point that is idle due to low network traffic,whereas MU-MIMO is effective when a plurality of UEs in one cell needsto simultaneously receive data due to heavy network traffic. Therefore,it is unusual that NC-JT and MU-MIMO are used at the same time, and theUE does not expect another UE in a cell to be simultaneously scheduledin an OFDM symbol at which a PDSCH for NC-JT is positioned and does notexpect a PDSCH for NC-JT to be scheduled in an OFDM symbol scheduledsimultaneously for a plurality of UEs, thereby significantly reducingthe complexity of the UE.

The methods for the UE to activate a receiver for only one of NC-JT andMU-MIMO at a specific time according to the embodiment may be summarizedas in a flowchart illustrated in FIG. 14.

FIG. 14 is a flowchart illustrating a method for a UE to activate areceiver for only one of NC-JT and MU-MIMO in order to reduce complexityaccording to an embodiment of the disclosure.

Referring to FIG. 14, the UE determines whether an NC-JT PDSCH isreceived (14-10). This process may be performed by a combination of oneor more of examples a or b described above. Alternatively, insingle-PDCCH-based NC-JT, the UE may determine whether an NC-JT PDSCH isreceived based on the number of beams indicated by DCI, for example, thenumber of TCI states indicated by a TCI codepoint. When the number ofTCI states indicated by the TCI codepoint is 2 or more, the UE maydetermine that an NC-JT PDSCH is received. When the number of TCI statesis 1, the UE may not determine that an NC-JT PDSCH is received.

When no NC-JT PDSCH is received, the UE operates an MU receiver toreceive data based on MU-MIMO (14-20). When the NC-JT PDSCH is received,the UE operates an NC-JT receiver to receive NC-JT data (14-30). Thisoperation may mean that the UE eliminates interference in the allocatedPDSCH, by itself

FIG. 15 is a block diagram illustrating the structure of a UE accordingto an embodiment of the disclosure.

Referring to FIG. 15, the UE may include a transceiver including areceiver 15-00 and a transmitter 15-10 and a controller 15-05 includinga memory and a processor. The transceiver including the receiver 15-00and the transmitter 15-10, and the controller 15-05, operate accordingto the foregoing communication method of the UE. However, components ofthe UE are not limited to the aforementioned examples. For example, theUE may include more components or fewer components than theaforementioned components. In addition, the transceiver 15-00 and 15-10,and the controller 15-05 may be configured as a single chip.

The transceiver including the receiver 15-00 and the transmitter 15-10may transmit and receive a signal to and from a base station. Here, thesignal may include control information and data. To this end, thetransceiver including the receiver 15-00 and the transmitter 15-10 mayinclude an RF transmitter to upconvert and amplify the frequency of atransmitted signal and an RF receiver to perform low-noise amplificationof a received signal and to downconvert the frequency of the receivedsignal. However, this is only an embodiment of the transceiver includingthe receiver 15-00 and the transmitter 15-10, and components of thetransceiver including the receiver 15-00 and the transmitter 15-10 arenot limited to the RF transmitter and the RF receiver.

In addition, the transceiver including the receiver 15-00 and thetransmitter 15-10 may receive a signal through a radio channel to outputthe signal to the controller 15-05 and may transmit a signal output fromthe controller 15-05 through the radio channel.

The controller 15-05 may store a program and data necessary for theoperation of the UE. The controller 15-05 may be implemented as at leastone processor. Further, the controller 15-05 may store controlinformation or data included in a signal obtained by the UE. Thecontroller 15-05 may include a memory configured as a storage medium,such as a read only memory (ROM), a random access memory (RAM), a harddisk, a compact disc (CD)-ROM, and a digital video disc (DVD), or acombination of storage media.

The controller 15-05 may control a series of processes such that the UEmay operate according to the foregoing embodiments. According to someembodiments, the controller 15-05 may control a component of the UE toreceive pieces of DCI of two layers, thus simultaneously receiving aplurality of PDSCHs.

FIG. 16 is a block diagram illustrating the structure of a base stationaccording to an embodiment of the disclosure.

Referring to FIG. 16, the base station may include a transceiverincluding a receiver 16-00 and a transmitter 16-10 and a controller16-05 including a memory and a processor. The transceiver including thereceiver 16-00 and the transmitter 16-10, and the controller 16-05, mayoperate according to the foregoing communication method of the basestation. However, components of the base station are not limited to theaforementioned examples. For example, the base station may include morecomponents or fewer components than the aforementioned components. Inaddition, the transceiver including the receiver 16-00 and thetransmitter 16-10, and the controller 16-05 may be configured as asingle chip.

The transceiver including the receiver 16-00 and the transmitter 16-10may transmit and receive a signal to and from a UE. Here, the signal mayinclude control information and data. To this end, the transceiverincluding the receiver 16-00 and the transmitter 16-10 may include an RFtransmitter to upconvert and amplify the frequency of a transmittedsignal and an RF receiver to perform low-noise amplification of areceived signal and to downconvert the frequency of the received signal.However, this is only an embodiment of the transceiver including thereceiver 16-00 and the transmitter 16-10, and components of thetransceiver including the receiver 16-00 and the transmitter 16-10 arenot limited to the RF transmitter and the RF receiver.

In addition, the transceiver including the receiver 16-00 and thetransmitter 16-10 may receive a signal through a radio channel to outputthe signal to the controller 16-05 and may transmit a signal output fromthe controller 16-05 through the radio channel

The controller 16-05 may store a program and data necessary for theoperation of the base station. The controller 16-05 may be implementedas at least one processor. Further, the controller 16-05 may storecontrol information or data included in a signal obtained by the basestation. The controller 16-05 may include a memory configured as astorage medium, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD,or a combination of storage media.

The controller 16-05 may control a series of processes such that thebase station may operate according to the foregoing embodiments.According to some embodiments, the controller 16-05 may control eachcomponent of the base station to configure pieces of DCI of two layersincluding allocation information about a plurality of PDSCHs and totransmit the DCIs.

While, the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents. Further, if necessary, theabove respective embodiments may be employed in combination. Forexample, any number of any of the embodiments of the disclosure may becombined to operate the base station and the terminal.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: receiving, from a firsttransmission and reception point (TRP), first downlink controlinformation (DCI) scheduling a first physical downlink shared channel(PDSCH) transmission; receiving, from a second TRP, second DCIscheduling a second PDSCH transmission, wherein the second PDSCHtransmission overlaps with the first PDSCH on a time-frequency resource;and receiving the first PDSCH transmission and the second PDSCHtransmission based on a first demodulation reference signal (DMRS)associated with the first PDSCH transmission and a second DMRSassociated with the second PDSCH transmission, wherein the first DMRSand the second DMRS are received on a same location within thetime-frequency resource.
 2. The method of claim 1, wherein at least oneof a starting position, a DMRS front-loaded symbol length, a DMRS type,a number of additional DMRS symbol, or a location of the additional DMRSsymbol are same for the first DMRS and the second DMRS.
 3. The method ofclaim 2, wherein at least one of a code division multiplexing (CDM)group or a DMRS antenna port, are different for the first DMRS and thesecond DMRS.
 4. The method of claim 3, wherein the first PDSCHtransmission and the second PDSCH transmission are data transmissions ofa non-coherent joint transmission (NC-JT) between the first TRP and thesecond TRP.
 5. The method of claim 4, wherein a multiple user (MU)multiple input multiple output (MIMO) is not applied to the terminal, incase that the data transmissions of the NC-JT are received.
 6. A methodperformed by a first transmission and reception point (TRP) in awireless communication system, the method comprising: transmitting, to aterminal, first downlink control information (DCI) scheduling a firstphysical downlink shared channel (PDSCH) transmission; and transmitting,to the terminal, the first PDSCH transmission based on a demodulationreference signal (DMRS) associated with the first PDSCH transmission,wherein second DCI scheduling a second PDSCH transmission is transmittedto the terminal from a second TRP, wherein the second PDSCH transmissionis transmitted to the terminal based on a second DMRS associated withthe second PDSCH transmission, wherein the second PDSCH transmissionoverlaps with the first PDSCH transmission on a time-frequency resource,and wherein the first DMRS and the second DMRS are transmitted on a samelocation within the time-frequency resource.
 7. The method of claim 6,wherein at least one of a starting position, a DMRS front-loaded symbollength, a DMRS type, a number of additional DMRS symbol, or a locationof the additional DMRS symbol are same for the first DMRS and the secondDMRS.
 8. The method of claim 7, wherein at least one of a code divisionmultiplexing (CDM) group or a DMRS antenna port, are different for thefirst DMRS and the second DMRS.
 9. The method of claim 8, wherein thefirst PDSCH transmission and the second PDSCH transmission are datatransmissions of a non-coherent joint transmission (NC-JT) between thefirst TRP and the second TRP.
 10. The method of claim 9, wherein amultiple user (MU) multiple input multiple output (MIMO) is not appliedto the terminal, in case that the data transmissions of the NC-JT aretransmitted.
 11. A terminal in a wireless communication system, theterminal comprising: a transceiver configured to transmit and receive asignal; and a controller configured to: receive, from a firsttransmission and reception point (TRP), first downlink controlinformation (DCI) scheduling a first physical downlink shared channel(PDSCH) transmission, receive, from a second TRP, second DCI schedulinga second PDSCH transmission, wherein the second PDSCH transmissionoverlaps with the first PDSCH on a time-frequency resource, and receivethe first PDSCH transmission and the second PDSCH transmission based ona first demodulation reference signal (DMRS) associated with the firstPDSCH transmission and a second DMRS associated with the second PDSCHtransmission, wherein the first DMRS and the second DMRS are received ona same location within the time-frequency resource.
 12. The terminal ofclaim 11, wherein at least one of a starting position, a DMRSfront-loaded symbol length, a DMRS type, a number of additional DMRSsymbol, or a location of the additional DMRS symbol are same for thefirst DMRS and the second DMRS.
 13. The terminal of claim 12, wherein atleast one of a code division multiplexing (CDM) group or a DMRS antennaport, are different for the first DMRS and the second DMRS.
 14. Theterminal of claim 13, wherein the first PDSCH transmission and thesecond PDSCH transmission are data transmissions of a non-coherent jointtransmission (NC-JT) between the first TRP and the second TRP.
 15. Theterminal of claim 14, wherein a multiple user (MU) multiple inputmultiple output (MIMO) is not applied to the terminal, in case that thedata transmissions of the NC-JT are received.
 16. A first transmissionand reception point (TRP) in a wireless communication system, the firstTRP comprising: a transceiver configured to transmit and receive asignal; and a controller configured to: transmit, to a terminal, firstdownlink control information (DCI) scheduling a first physical downlinkshared channel (PDSCH) transmission, and transmit, to the terminal, thefirst PDSCH transmission based on a demodulation reference signal (DMRS)associated with the first PDSCH transmission, wherein second DCIscheduling a second PDSCH transmission is transmitted to the terminalfrom a second TRP, wherein the second PDSCH transmission is transmittedto the terminal based on a second DMRS associated with the second PDSCHtransmission, wherein the second PDSCH transmission overlaps with thefirst PDSCH transmission on a time-frequency resource, and wherein thefirst DMRS and the second DMRS are transmitted on a same location withinthe time-frequency resource.
 17. The first TRP of claim 16, wherein atleast one of a starting position, a DMRS front-loaded symbol length, aDMRS type, a number of additional DMRS symbol, or a location of theadditional DMRS symbol are same for the first DMRS and the second DMRS.18. The first TRP of claim 17, wherein at least one of a code divisionmultiplexing (CDM) group or a DMRS antenna port, are different for thefirst DMRS and the second DMRS.
 19. The first TRP of claim 18, whereinthe first PDSCH transmission and the second PDSCH transmission are datatransmissions of a non-coherent joint transmission (NC-JT) between thefirst TRP and the second TRP.
 20. The first TRP of claim 19, wherein amultiple user (MU) multiple input multiple output (MIMO) is not appliedto the terminal, in case that the data transmissions of the NC-JT aretransmitted.